Concept: Bond order is a measure of the number of chemical bonds between two atoms. It can be calculated using molecular orbital theory. For diatomic molecules, a simple shortcut is to count the total number of electrons and use the following relationship:

• 14 electrons = Bond order 3
• 13 electrons = Bond order 2.5
• 12 electrons = Bond order 2
• 11 electrons = Bond order 1.5
• 10 electrons = Bond order 1
• 15 electrons = Bond order 2.5
• 16 electrons = Bond order 2
• 17 electrons = Bond order 1.5
• 18 electrons = Bond order 1

Why (A) is correct: We need to calculate the total number of electrons for each species and then determine their bond order.

Step 1: Calculate total electrons and bond order for each option.

• A) CN^-: Carbon (6 e^-) + Nitrogen (7 e^-) + 1 (for negative charge) = 14 electrons.
  Bond order = 3.
• B) NO⁺: Nitrogen (7 e^-) + Oxygen (8 e^-) - 1 (for positive charge) = 14 electrons.
  Bond order = 3.
• C) O₂^-: Oxygen (8 e^-) + Oxygen (8 e^-) + 1 (for negative charge) = 17 electrons.
  Bond order = 1.5.
• D) O₂^2-: Oxygen (8 e^-) + Oxygen (8 e^-) + 2 (for negative charge) = 18 electrons.
  Bond order = 1.

Step 2: Compare bond orders.

Both CN^- and NO⁺ have a bond order of 3. Therefore, they have identical bond orders.

Option Analysis:

• A) CN^-: Bond order = 3.
• B) NO⁺: Bond order = 3.
• C) O₂^-: Bond order = 1.5.
• D) O₂^2-: Bond order = 1.

Since the question asks which of the following have identical bond order, and options A and B both have a bond order of 3, the question implies selecting one of the options that has an identical bond order to another option. Given the options, CN^- and NO⁺ are the pair with identical bond orders. If this were a multiple-choice question where only one answer could be selected, and the question was phrased as 'Which of the following has an identical bond order to X?', then X would be the reference. As phrased, it asks 'Which of the following have identical bond order?', implying a pair. However, in standard MCQ format, one option is usually the 'correct' one. If the question implies finding a pair, then both A and B are part of that pair. If it's a single-choice question, there might be an ambiguity. Assuming the intent is to identify a species that shares a bond order with another listed species, both A and B fit. Since the provided correct answer is A, it implies that A is one of the species in the pair with identical bond order.

Correct Answer: (A)